The present invention relates to a bistable two position selector valve that includes a switching mechanism that prevents the valve from being placed in any stable intermediate position between its normal two remote positions.
There are many types of multi-position valves that are moveable between two positions and which are designed to avoid, to the extent possible, any stable intermediate position where the exact valve position is ambiguous. That is, in many valve applications it is important that the valve be switched between its two positions in a positive manner and that the operator is unable to leave the valve in some mid position where, for example, two inlets or outlets may be open. This is particularity true in medical applications where an operator needs to know that the path of the flow of gas is the one selected.
Typical valve mechanisms include over-center springs such as are commonly used on toggle switches and which cause the valve or switch to rapidly move from one position to the other position when the valve operator reaches a certain point in its movement.
In such cases, however, there is still a possibility that a user could move the toggle mechanism to such a position that the valve is in midstream, caught or at least momentarily held in a position not desired by the operator nor apparent from the position of the mechanism. In most such over-center spring mechanisms, an operator can thus inadvertently place the valve in an ambiguous position.